Make-busy arrangement for secondary trunking switches



June 9 1,540,159

. J. I. BELLAMY MAxE'BusY ARRANGEMEM FOR SE'CONDARY'TRUNKING SWITCHES Filed Aug. 25. 2

inure/z TAKi BE 0 Inu' snlnr Jbhn LE Enemy Patented June 2, I925.

UNITED STATES PATENT OFFICE;

JOHN L BELLAMY, OFYCHICAGO, ILLINOIS, ASSIGNOH, TO AUTOMATIC ELECTRIC COM- PANY, OF'GHIGAGO, ILLINOIS, A CQRPORA'IIOII OF ILLINOIS.

MAKE BUSY ARRANGEMENT FOR SECONDARY TRUNKING SWITCHES.

Application filed August 25, 1922. Serial Ho. 584,218.

To all 107mm it may concern.

Be it known that I, dorm I. BELLAM'Y, a citizen of the United States of America, and

a resident ot Chicago, Cool: County, and State of Illinois, have invented certain new and useful Improvements in Make-Busy Arrangements for Secondary Trunking Switches, of which the following isa specification. V

The present invention relates to make busy arrangements for secondarytrunking switches, but is concerned more'particularly with secondary trunking systems for telephone systems in which a secondary group is made busyimn'ieoiately upon the last trunk :Klt sible thereto being seized.

This case in some respects is an improvement on a make: busy scheme disclosed in the co-pending application of Richardson, serial No. 507,009, filed October 11, 1921. p

In order to be able to make a subgroup of secondary switches busy as soon as. the last trunk accessible thereto is seized, it has been proposed to arrange the circuits of the secondary switches so that the release trunk conductors of all the idle secondary switches of the sub-group are normally multipled together and extended to a common relay,

which relay is arranged topull up each time.

a trunk is seized and to lock to ground when the last trunk accessible to the secondary switches is seized, thereby making the remaining idle secondary switchesbusy. A circuit whichaccomplishes this result in the above manner is in many cases objectionable :l'oithe reason that, since the release trunk conductors otnll the idle secondary switches are niultipled together, the entire subgroup is made busy while one secondary switch therein is hunting for anidle trunk. This feature is rendered less objectionable in the present case by suitably arranging the circnits so that th release trunk conductors of the idle switches are not normally connected together, but are connected together as soon as all the secondary trunks except a small predetermined number become busy. In this way, as many secondary switches as desired may be seized. at one time until the, number of trunks accessible thereto and remaining idle becomes very small, at which time the release trunk conductors of the idle switches are multipled together, giving the protection desired by rendering the entire subgroups.

trunks, namely, fl 'teen.

group oi secondary switches busy as soonas the last trunk is taken.

Referring now to the drawings which comprise Figs. 1 and 2, Fig. 1 shows a selector which has access on one level to the secondary switch C. The secondary switch C has access to the repeater R The two conductors extending from the repeater R are assumed. to extend to a distant ofiicc and terminate in an incoming selector.

The trunking arrangement perhaps can be understood a little better by referring to F 2, which shows ten selector trunks on the left. which extend to ten secondary switches in as many 7 different secondary The third trunk is illustrated as entending to the secondary switch C which is the same switch as shown in Fig. 1. The s itch C is shown as having'accessto ten re= pe'aters, Rr inclusive, although in practies the number may be either larger or smaller than this. As one instance or the size of the entire secondary group, it may be assumed that there are fifteen groups of selector trunks comprising ten trunks each.

()ne'of these groups ofselector trunks is shown in Pig. 2, and, as 1ndicated,feach selector trunk extends to a separate one of the ten secondary subgroups. The same applies for each of the other fourteen groups of selector trunks l-rccordingly, considering any one secondary sub-group, for example, the one in which the secondary switch C is located, there are as many secondary switches'as there are groups of selector Accordingly, the multipling relay 101, Fig. 1, is proyided with three armatures 107, 107", and 108, having five working contacts each, making fifteen contacts in all, one for each of the fifteen secondary switches, such as C, in the same sub-group.

Inthe lower partot Fig. 1, there is shown a group of relays which are the ones which have to .do with making the secondary group, in. which the secondary switch C is located, busy when the last available trunk is taken. 1

Perhaps the invention will be understood best it a brief description of the operation of the apparatus shown is given. F or this purpose, it will be assumed that the selector E is seized at theterminals ll, 12, 2 id 13.

lVhcn this occur-shire relay 'li' energizes digit of the desired number, the circ number Ofti1l'iS. Each ,tiineline relay 1 V ergizedin series with verti-:=almagnet .over conductors 1st and 16, in series with the calling subscribers loop, andcloses a circuit'for release relay 18 at armature 28. Release relay 18, upon energizing, opens a point in the circuit of release magnet it and prepares acircuit for vertical niagnet22 at armature 30, and at armature 29 places ground-on release trunk conductor 15, thereby establishing the usual holding circuit. for the switch which seizedth'e selector.

When the calling subscriber operates his calling device in accordancewith the first it of line relay 1? is opened a correspor "a T .deenergizcs, it sends-an impulse of current to vertical n agnetQQby way of armature SO and its working contact and series relay 19. By the operation of vertical magnet the switch wipers 3S l9, inclusive, are raiseth opposite thedesiredlevel of banl: cont acts. Slow acting series relay '19 is maintained ens throughout the vertical movement and, .in conjunction with off. norinal contac s 26, which close upon the first vertical step, closes Y a circuit tor-stepping relay 20in series with interrupter contacts 27'. Relay 2i), uponenergizing, closes alockingcircuittor. itself at, armature 32, and at armature prepares a circuit for rotary magnet 23.

7 At the end otthe verticalmovement, relay 19 deencrgizes and closes the circuit Orr-0s.

tary magnet 23. Rotary magnet 23, upon energizing, advances the switch wipers into: engagement with the first set o't bani; contacts in the level opposite which they are raised, and, near the end of itsstroke, opens.

the circuit of stepping relay 29 at interrupter contacts 27." Steppmg relay 20,vup.on i

, deenergizing, opens the circuit of v rotary V ues until an idle trunk is reached,,avhicln trunlcit will'be. assumed is'the one extend-- ing to the secondary switch C. 'Wnen this occurs switcliing relay 21, being no longer short circuited, energizes series with step ping relay 20, thenlatter relay not energizing on account of the high resistance of switching relay i 21. Upon energizing, switching relay 2l-rernoves ground ironiarmature H8 or line relav 17 at armature 3'5,

thereby opening the circuit of release relay 18; opens the test circuit and prepares the holding circuit at armature- 35, thereby grounding test wiper 39 and making the seized trunk lines busy immediately; and at arinatures 34 and 37 disconnects conductors 14 and 16 from the windings of line relay 17 and extends them byway 0t wipers 3S and 40, bank contacts 41 and i3, conductors 1 4A and 46, and armatures 64 and (3? and their resting contacts to the winding of line relay .58 and ground,- respectively.

Line relay 58 ofthe line switch C, upon energizingoverthe callingsubscribers loop, places ground on releas trunk conductor, at armature 63, I thereby establishing v the usual holding circuit for the selector E through bank contact 42 and test wiper 39 before release relay 18 has had time to deenerglze. As a further result of theaener- .glZa-tlOIL of'relay 58, it closes a circuit for switching relay, 59 andstepping magnet 60 inv series at armature 62 and at'armature 61 connects test wiper 69to the junction of switching relay 59 and stepping magnet (30.

In case the trunk uponwhich the wipers ot the switch are standing is busy, switching relay 59 is short circuited by the ground potential which is present on the test contact thereof and the'wipers 6870, inclusive, are

. advanced-in -search of an idle trunk by the buzzer-like action of stepping magnet. 6(), which magnet operates from ground on the busy test contacts. In the present case, however, it will be" assumed that the trunk upon which the wipers of the switch are standing isgid-le. '='Thatbeing the case, switchingrelay 59 isnot'short circuit'ed and,upon energizing in serieswithstepping magnet 60, which ,rnagnet does not energize under these conditions on account of the high resistance. of switching relay 59, connects release trunk conductor l5 t0 the winding of switching relay. 59 at armature 66, opens the test circuit and prepares the holding circuit at :11-

mature 65,, and at armatures 64 and 67 disconnects conductors A and $6 from the winding of relay 58 an'd from ground and extends them by way oi wipers-68 and 70, conductors 71 and 73, and the left-hand aviiicliiigs of the repeating coil to the wind ings of the line relay 80 ot the repeater R Line relay 80, upon energizing, closes a bridge across the outgoing trunk conductors at armature 83, whereupon the distant selector is prepared for operation in the usual manner, and at armature 82 closes a circuit for release relay 81. Release relay 1, upon ener izing, short circuits the resistance 86 in the make busy chain circuit at armature Si"), and at armature 84 places ground on the release trunk conductor 72, thereby establishing the usual-holding circu'itwfor the switches E and C before the slow actinglinerelay 58 f the swltch Chas had tune to deenergize;

The calling subscriber now operates his calling device in accordancewith the re maining digits of the desired number, whereupon line relay 80 ot the repeater R 1 repeats the interruptions of the calling device at armature 83, and the connection is extendedto the desired line 'i'n' the usual manner. When "the calling subscriber replaces his receiver upon the termination of 1' the ensuing conversation, line relay 80, upon deenergizing, opens the circuit of the distantline relay at armature and at armature 82 opens the circuit of release relay 81. Release relay 81, upon deenergizing, removes the shunt from around resistance 80 at ar-f mature 85 and at armature, 8 1 removes ground from release trunk conductor 72,

whereupon switching relays 59 and 21 of the switches C and E deenergize. Switch ing relay 21 of the selector E, upon deenermanner and the circuit of release magnet 21 is again opened at off normal contacts lleterrlng now to the make busy equipment comprising the relays shown 1n the lower part ct vFig. 1, it will be noted thatthe release trunk conductors of the idle secondary Q-SWI CCl1GS such as C extend to the contacts of relay 101, but are not connected together -15 1 07, 107 and 108.

. force the calls to come into thls ti l eat' normally. is the secondary trunks become busy one by one, the resistances such as 86 and 89 are short circuited without. producing any particular effect until only two secondary trunks are idle, at which time only two of the resistances will remain unshunted, which resistances itwill be assumed are 86 and 89. lVhen this occurs, the marginally adjusted relay 103 energizes'and closes a circuitfor relay 101. at armature 111. Relay 101, upon energizing," connects the release trunk conductors of all the idle switches in this group together at armat-ures This is done to a time. W hen the next callcomes in, ground is placed on the releasetrunkconductor 'ot the trunk seized by theseizing switclrwhen 59 the swltchlng relay thereot energizes, such as for example, at armature of switching relay 21 of the selector E. This makes the entire group of switches busy immediately and holds the group busyuntil the seized secondary switchcuts through and disconnects its: release trunk conductor such as tor example, at armature66 of relay 59 ot the secondary switch C. When this occurs, the group is rendered idle again. Relay 102 18 energized during the time that the secondary switch is hunting but does not have any ettect. When the line and release relays of the seized secondary trunk energize, one of the remaining resistances, resistance 86 for ex- (35 ample, is short circuited, whereupon the marginally adjusted relay 1041 energizes and connects ground to the working contact of armature 109 of relay102 at armature 112.

energizes and places multiple ground on armatures 107, 107 and 108 at armature 113, and at armature 11 1 closes a cu'curttor relay 106. Relay 106 upon energizing, closes a lockingcircuit tor'itselt' at armature 116 by way of armature 110 and its working contact, and at armature 115 opens the locking circuit of relay 109, leaving relay 109 energized and the release trunlrconductors of theidle switches grounded-by way of the working contact'ot armature 113 and said armature. The circuits remain in this condition until one secondary trunk becomes idle; When this occurs, relay 105 falls bael; opens the initial circuit of relay 100 at armature 11 1; and at arinature'll opens the circuit of relay 102 and renders the group available again. Relay 102, upon deenergizing, opens a point in its previously closed locking circuit at armature 109, and at arresistances, such as or 89. Upon deenergizing, relay 10 1 opens a point in the loclc ing circuit of relay 102 at armature 112.

Incase still another trunk becomes idle, relay 103 deenergizes and opens the circuit of relay v101 at armature 111, whereupon the various release trunk conductors of the idle switches in this group are separated at armatures 107,107 and 108. a

lVhat is claimed is:

1. In a telephone trunkingsystem, a plurality of incoming trunks, each trunk terminatin in a switchin 'mechanism a lesser Z3 13 7 plurality of outgoing tllll'llIS accessible n common to all said mechanisms, each of said i incoming trunks havlng a test conductor,

said conductors being disconnected from each other, and means effective whenever there are only a predetermined number of outgoing trunks idle for connecting together :the test conductors of "all the idle incomin trunks. I

2. In a telephone trunking sy stem, a plu- "rality of incomingtrnnks, each terminating in switching; mechanism, alesser plurality of outgoing trunks. accessiblein common 'to all-said mechanisms, each of saidiincoming' trunks having a test conductor; saidiconduc-v. ,tors being disconnected from: each other, queens-effective whenever gthereware only a I predetermined number of outgoing trunks idle .tor. connecting togetherithe test- -conductors of all the idle incomingtrunks, and

.meanseflective whenever there 'is only one idle-outgoing trunk io'nplacing a guarding potential-on the test =conductors'ot' all the idle incoming, trunks when the next incoming trunk is taken for use."

3. In a primary' and socondary telephone ----t runl;r'mg system Hi1- which the remaining idle primary trunks arc allrendered non-selectable :imn'iediatelyi upon 3 seizure of any primary trunkwhen: there is only one secondary trunkavailable, and in which the primary trunksare heptbusyfuntil another secondary trunk becomes a/Vii1luble,-:a test conductor for each primary trunk-,saidconductors being disconnectedfrom each: other,

:and means under thecontrol oii'th'e seconctary trunks for connecting together all test conductorsrot the idleprimary trunkswhenever there are onlypredetermined number of secondary trunks remaining idle.

4; In a make busy circuit, three relays, a.

means con-trolled over said trunks for operating the first-of said 'relayswhenever only. two ofsaid; trunks are idle, fonoperatmg these'condzot-said relays whenever-onlyone of said trunksis idle,- and' for-operating the third of saidrelaysrwhenever none of said trunks are idle. v 1

In a telephone system, niea1'1s-forbusying automatic switchescomprising a circuit,

a series of resistances1-.includedin said circuit, means for separately short circuiting said resistances, a relay in said; circuit-1esponsive to the short circuiting of all said ;resistances except one, and another relay in said- CllCLlitlGSPODSlVG'ODly'tO the short on"- cuitingof all said resistances 6.111 a telephone, systein means forfbusy ing automatic switches comprising a circuit, a series of resistances included iii-said circuit, means for separately short 'circulting said resistances, arelay-iins'aid circuit responsive to the short circuiting of all said :resistances except two, and: another relay 1n said circuitresponsive-only to the ShQItYClI- cuiting of all said: resistances.

-. 7 In a telephone system, means for busyingautomatic switches i-comprising-- a ci.r-.

King .in said switches, trunkl lines accessible to said switches, and means responsive to the busy condition of a predetermined number of said trunklinesfor connectlngthe release trunk conductorsassociated with idleones i of saidswitches together.

9. In a ;-tel ephone system, a. group of switches, release trunk conductors terminat-f ingin said'switches, trunk lines: accessible to said switches-,=-andmeans responsive when allbut two of said trunkl lines become busy for connecting together all-of said release trunk conductors except those associated withbusy switches. V 7

-10. In a telephone system, agroup of switches, release trunk conductors terminating in said switches, trunk liues accessibleto said switches, relaymechanisin for connecting together therelease trunk conductors associated withidle ones otsaid switches, and

circuit arrangements whereby said mechanism is placed under the. joint control or a plurality of -said' trunk lines. I

11. lnatelephone system, a group of automatic trunking switches a group of trunk lines accessible to said switches, acircuit for rendering all idle switches busy responsive :to the seizure-of one of said switches, and meansfor closingsaid circuit only when a given: pulrality of-said' trunk lines arelin "use. i s

-12. In:a telephone system, a plurality of iincoming trunks each I,-termin'ating in a switching mechanism, a lesser plurality of outgoing trunksz'accessible in common to all said mechanismsiand means for busying the excess incoming: trunks when" the outgoing atrunks :are all: in use, said n' eans including three. relays-with means for energizing one u'elay when-all "but two of said outgoing trunks are busy, zmeans "for energizing another of the. relays vwhen all but:one of said outgoingv trunks are busy,,and means for energizing the other relay when all of .;said outgoing: trunksare busy. I

In Witness whereofjll hereunto subscribe r my name: this 21st ,dayqoff-August, A."D.,

l-JOI-IN I. BELLAMY.

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